Effects of respiratory muscle training on swimming performance, respiratory muscle function, and pulmonary function of competitive swimmers: a systematic review and meta-analysis

Background Competitive swimming imposes unique physiological demands on the respiratory system. While respiratory muscle training (RMT) is proposed to optimize respiratory function and athletic performance, its efficacy in competitive swimmers remains inconsistent. Objectives This systematic review and meta-analysis evaluated the effects of RMT on respiratory muscle function, pulmonary function, and swimming performance in competitive swimmers. Methods Eight databases were searched from inception to 26 September 2025. Inclusion criteria were: (1) RMT interventions (inspiratory, expiratory, or combined) lasting ≥4 weeks; (2) participants were elite or high-level competitive swimmers; (3) control groups received sham RMT or standard training; and (4) outcomes included swimming performance, respiratory muscle strength, or pulmonary function. Methodological quality was assessed using Cochrane RoB 2.0 and the GRADE framework. Results A total of 14 studies involving 375 competitive swimmers were included. The meta-analysis indicated that RMT significantly improved maximal inspiratory pressure (MIP) (SMD = 0.65, 95% CI: 0.29 to 1.01, p = 0.001) and certain dynamic pulmonary function parameters (forced expiratory volume in 1 s [FEV1], SMD = 0.45, 95% CI: 0.19 to 0.72, p = 0.001; forced inspiratory volume in the 1st second [FIV1], SMD = 0.41, 95% CI: 0.04 to 0.79, p = 0.03), as well as aerobic swimming performance (SMD = 1.02, 95% CI: 0.03 to 2.00, p = 0.04). In contrast, RMT did not significantly improve maximal expiratory pressure (MEP) (SMD = 0.16, 95% CI: −0.14 to 0.46, p = 0.30), other pulmonary function outcomes (forced vital capacity [FVC], maximal voluntary ventilation [MVV]), or sprint and middle-distance swimming performance (50 m, 100 m, and 200 m freestyle times, p > 0.05). Conclusion RMT effectively enhances respiratory muscle strength and dynamic lung function in competitive swimmers across diverse levels, particularly with combined RMT demonstrating superior efficacy over IMT alone. Regarding athletic outcomes, RMT shows limited efficacy in enhancing short-distance swimming performance, while it exerts a significant positive impact on aerobic performance; however, its potential benefits require cautious interpretation due to high inter-study heterogeneity. This study offers updated insights into RMT’s role in aquatic conditioning, emphasizing the need for future load-matched trials to isolate its independent effects. Systematic Review Registration https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42024503624 , identifier CRD42024503624.